We are not out of the woods yet. Although some societies are starting to reopen, others, such as the UK and Spain, have extended lockdowns to try to bring the Covid-19 pandemic to heel.

But what if this lasts for months or even years to come? That is the unnerving prospect raised by a paper published last week. Scientists at Harvard University suggested that periods of social distancing may be required until 2022 and possibly beyond, if hospitals are to avoid becoming overwhelmed by future waves of infection. If treatments and vaccines do not arrive quickly, we may need to steel ourselves for prolonged economic and social disruption.

One early hope was that the virus would burn itself out, as happened in the Sars epidemic, thanks to an unprecedented public health effort. Middle East respiratory syndrome, caused by a related but even deadlier coronavirus, has also shown limited spread.